The present invention relates to techniques for data backup and recovery.
Known storage system backup/recovery methods include a method referred to as CDP (Continuous Data Protection). In this method, data history is accumulated as a series of journals and, when recovery becomes necessary as a result of malfunction or operation failure, the accumulated journals can be employed to perform restore operation resulting in a data image of any point in time.
For example, cited reference 1 (Japanese Unexamined Patent Application No. 2004-252686) discloses a system that actualizes CDP. When data update from a host is performed, a storage system acquires update data and pre-update data to a journal volume of a disk and, furthermore, creates an association between a data set and an identifier. When restore is performed, the identifier associated with the data is employed to facilitate restore to a specified point in time. As the result, restore that does not substantially load the resources of the host can be performed.
There has been a dramatic increase in the use of electronic data that must be kept for a long period and, of the forensic-related data thereof, very complete journal data must be recorded. A problem inherent to conventional disk-based CDP is the excessive capacity and related cost created by the continuous acquisition of complete journal data to disks. Furthermore, because the disk capacity is limited, when an overflow of acquired data occurs, previous journal data must be deleted. Accordingly, there is a problem whereby only short-period segments of data can be kept.
A method based on the storing of journal data in a tape by a host has also been developed. However, this method suffers from a drawback in that a large load is placed on the host that leads to a lowering of host performance. In addition, this method gives no consideration at all to restore efficiency from the tape. The application of this method is not restricted to tapes and it may be similarly implemented in other types of sequential access-type storage device (storage devices of a type in which high-speed sequential access processing is possible but high-speed random access processing is not possible).